Camera system for hazardous environments

ABSTRACT

A camera system is provided for use in a high-radiation environment includes a camera assembly with a housing enclosing an image sensor for generating a digital signal of a detected image and a first serializer/deserializer (SERDES) for converting the digital signal from the image sensor into a serial bit stream. A transmission medium transmits the serial bit stream to an image processing module located outside of the high-radiation environment where a second SERDES deserializes the serial bit stream to generate a decoded image signal which is processed by an image processor to generate an output at a display device corresponding to the detected image.

RELATED APPLICATIONS

This application claims the benefit of priority of U.S. ProvisionalApplication No. 61/590,525, filed Jan. 25, 2012, which is incorporatedherein by reference in its entirety.

FIELD OF THE INVENTION

The invention relates generally to industrial video cameras, and moreparticularly to industrial video cameras for nuclear power plantmonitoring and other applications that require radiation hardening.

BACKGROUND OF THE INVENTION

Nuclear plant operators and service companies perform in vessel visualinspections (IVVI) in conjunction with reactor refueling operations toinspect reactor components for flaws or damage to the reactor vessel andcomponents within the reactor including submerged pipes and bores. Forexample, a reactor pressure vessel (RPV) of a boiling water reactor(BWR) typically has submerged bores that need to be inspected duringmaintenance routines. Hollow tubular jet pumps having internal bores arepositioned within an annulus to provide the required reactor core waterflow. During operation of the reactor, components including their weldjoints within the reactor can experience inter-granular stress corrosioncracking (IGSCC) and irradiation assisted stress corrosion cracking(IASCC) which can diminish the structural integrity of the reactorcomponents, such as jet pumps, by way of example. It is important toperiodically examine the reactor core components and all welds containedtherein to determine whether any cracking or failure has occurred.

The ability to accurately and quickly perform the IVVI visualinspections can impact the outage associated with the nuclear reactor.Thus, improvements to the accuracy and speed with which visualinspections can be performed can reduce the outage period and save thenuclear plant operator significant expense.

A visual inspection system typically includes one or more cameraspositioned on a remotely operated vehicle that can be moved to variouslocations within the reactor vessel. Each camera is coupled to a videotransmission system that provides an image signal to a remotely locatedvisual display device or storage system. These visual systems are usedto inspect the reactor components for damage and/or to look for debristhat may have accumulated in the reactor. A number of cameras are usedfor various tasks including inspections of the outer surface of pipesand inner bores of pipes, apertures and bores. Generally, each visualinspection system (camera, transmission system, and display) is requiredto meet predefined imaging standards to ensure that the visualinspection is capable of identifying and delineating the necessaryspecificity in flaw and damage identification. The requirements for IVVIvisual inspection systems include visual Testing (VT) standards such asa rigorous EVT-1 standard, by way of example. The EVT-1 standardprovides that the imaging system be capable of resolving a 0.0005″ (½mil) wire on an 18 percent neutral gray background. The EVT-1 standardas well as other known visual inspection standards rely on personalevaluation by an operator to ensure that the imaging system is providingthe appropriate image quality to the remote display from which theinspection is performed. Any inconsistencies can result in the failureof the visual inspection system in providing an image for viewing inwhich the operator can identify a potential flaw or damage which canresult in failure to identify such, or can require re-inspection, andtherefore added time and costs for the IVVI inspection.

Several systems have been developed for performing IVVI inspection. Anexample of currently available systems is the Diakont D40 Camera(Diakont Advanced Technologies, San Diego, Calif.), which is consideredto be state-of-the-art for visual inspection. This system uses a tubesensor that generates a monochrome image that is converted to colorthrough the use of colored LEDs, which are used to illuminate the areaunder inspection in a rapid sequence. A computer program uses the colorsto convert the monochrome image into color. Even though the sequencingof the colored LEDs is rapid, the cycling of the LEDs, along with theprocessing time, results in delays that may be manifested as blurredimages when the camera is moved. This can be problematic when resolutionis important for identifying small defects. Further, the use of a tubelimits the size of the camera, preventing the miniaturization needed forclose inspection in tightly spaced structures.

Another drawback of existing systems is that the camera sensor, whethertube or solid state (e.g., CCD, CID, CMOS), produces an analog signalthat is communicated to the image processing system. The use of analogsignals presents a disadvantage since the signal must be digitizedwithin the processor, often requiring additional processing to interpretthe image using statistical methods. While many such techniques canproduce good results, the additional processing can produce delays thatextend the time required for accurate inspection.

Accordingly, the need remains for a radiation-hardened camera that canbe used for high resolution visual inspection of high radiationenvironments such as nuclear reactors.

SUMMARY OF THE INVENTION

In an exemplary embodiment, a camera for visual inspection comprises asensor for producing a digital signal corresponding to detected images,where the camera is disposed within a housing along with appropriatedriver electronics and a serializer-deserializer (SERDES)encoder/decoder. The SERDES converts the signal from the sensor into ahigh frequency bit stream which is communicated through an appropriateconnector to a high frequency cable, e.g., a microwave cable, to aprocessing module in which a second SERDES receives the high frequencysignal and resolves the incoming bit stream into a digital bit streamfor processing of the image. The use of a SERDES encoder/decoder pair,one at the sensor and one at the processing module permits high speedtransmission of data from the sensor to the processing module andcontrol commands from the processing module to the sensor.

In one aspect of the invention, a camera system is provided for use in ahigh-radiation environment, where the camera system includes a cameraassembly comprising a housing, an image sensor disposed within thehousing, the image sensor adapted for generating a digital signalcorresponding to a detected image of an object, and a firstserializer/deserializer (SERDES) disposed within the housing forconverting the signal from the image sensor into a serial bit stream; atransmission medium for transmitting the serial bit stream; and an imageprocessing module disposed outside of the high-radiation environment forreceiving the transmitted serial bit stream, the image processing modulecomprising a second SERDES adapted for deserializing the serial bitstream to generate a decoded image signal; and an image processoradapted to process the decoded image signal to generate an output at adisplay device corresponding to the detected image. In one embodiment,the housing includes a seal for enclosing the image sensor and the firstSERDES within a watertight enclosure. The housing may optionally beformed from stainless steel, and may include

radiation shielding that encloses one or more of the image sensor andthe first SERDES.

In another aspect of the invention, a camera system is provided for usein a hazardous underwater environment, where the camera system includesa camera assembly comprising a housing having a watertight seal, animage sensor disposed within the housing, the image sensor adapted forgenerating a digital signal corresponding to an image of an objectlocated within the underwater environment, and a firstserializer/deserializer (SERDES) disposed within the housing forconverting the signal from the image sensor into a serial bit stream; atransmission medium for transmitting the serial bit stream; and an imageprocessing module located away from the hazardous underwater environmentfor receiving the transmitted serial bit stream, the image processingmodule comprising a second SERDES adapted for deserializing the serialbit stream to generate a decoded image signal, and an image processoradapted to process the decoded image signal to generate an output at adisplay device corresponding to the image of the object. In oneembodiment, the housing is formed from stainless steel and may includeradiation shielding enclosing one or more of the image sensor and thefirst SERDES. The camera system may further include a robotic deliverysystem responsive to a controller located away from the hazardousunderwater environment.

In one embodiment, the sensor is a CMOS Image Sensor. For nuclearreactor inspection applications, the image sensor is preferablyradiation hardened to operate without significant signal degradation upto 2 MRad TID (total integrated dose). Other types of sensors, includingCCD and CID, may be used as long as the sensor produces a digital bitstream that is provided to the SERDES for transmission to the processingmodule. The sensor and SERDES may be enclosed within a watertighthousing that is suitable for operation in water. For nuclear reactorapplications, the material used for the housing is preferably stainlesssteel. Some level of radiation shielding may be included in the housingwith a trade-off between size versus camera life, since the moreshielding that is used, the larger the camera head will be. In oneembodiment, the sensor itself may be unshielded, while the SERDES chipand associated components may be shielded. Since it is a significantadvantage of the inventive system to provide a very small camera headthat can be used to inspect tight spaces, increasing the dimensions ofthe camera head by adding shielding should be considered carefully.

In one embodiment, the camera housing may be mounted on a roboticdelivery system that is remotely controlled from the processing module.(Note that control signals for the robot may also be carried over thehigh frequency cable.) A watertight connector or penetrator providesconnection to a high frequency (e.g., microwave or faster) cable. Strainrelief should preferably be provided to avoid damaging or stressing thecable when the robot moves. The cable may be on the order of 50 feet orlonger to provide sufficient isolation from the radiation source. Theprocessing module may be housed within a workstation with data storagefor storing the collected video (both raw and processed) and a userinterface such as a monitor or other graphic display that allows theoperator to observe in real time and to control movement of the robot toinspect the area of interest.

While significant advantage is gained through use of the presentinvention for visual inspection of nuclear reaction, the invention isnot intended to be limited to such applications. The principles of theinvention are applicable to other sensor types and differentenvironmental situations. Such other uses for the system describedherein will become apparent to those of skill in the art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an exemplary system for visual inspectionof a nuclear reactor vessel.

FIG. 2 is a block diagram of the sensor and processor.

FIG. 3 is a block diagram of an integrated circuit verification process.

FIG. 4 is a block diagram showing remote in-system operation.

FIG. 5 is a block diagram of the present invention showing multiple nodearchitecture.

DETAILED DESCRIPTION

As illustrated in FIGS. 1 and 2, the camera 10 for visual inspectioncomprises an image sensor 20 for producing a digital signalcorresponding to detected images, where the camera comprises a housing22 for supporting lenses and/or windows 26 along with appropriate driverelectronics 24 and a serializer-deserializer (SERDES) encoder/decoder12. The SERDES converts the signal from the sensor into a high frequencybit stream that can be communicated through an appropriate connector toa high frequency cable 28, e.g., a microwave or faster cable, to aprocessing module 30 in which a second SERDES 32 receives the highfrequency signal and resolves the incoming bit stream into a digital bitstream for processing of the image by image processor 34. The use of aSERDES encoder/decoder pair, one at the sensor end and one at theprocessing module 30 permits high speed transmission of data from thesensor to the processing module 30 and control commands from theprocessing module to the sensor.

In one embodiment, the sensor 20 is a CMOS Image Sensor. For nuclearreactor inspection applications, the image sensor is preferablyradiation hardened to operate without significant signal degradation upto 2 MRad TID (total integrated dose). Other types of sensors, includingCCD and CID, may be used as long as the sensor is capable of producing adigital signal that can be provided to the SERDES 12 for high frequencytransmission to the processing module 30. In the preferred embodiment,the sensor is a radiation hardened color sensor. In other embodiments,the sensor may be a radiation hardened monochrome sensor with the imagecolor being generated during image processing based on different colorLEDs that are placed on or in the camera. While such an approach tendsto insert delays into image processing when used in prior art systems,the impact is reduced in the present invention due to the high frequencydata transmission made possible by the use of SERDES encoders/decoders.The sensor and camera SERDES 12 may be enclosed within a watertighthousing 22 that is suitable for operation in water. For nuclear reactorapplications, the material used for the housing is preferably stainlesssteel Some level of radiation shielding may be included in the housing22 by trading off size versus camera life, since the more shielding thatis used, the larger the camera head will be. In one embodiment, thesensor 20 may actually be unshielded, while the SERDES chip 12 andassociated components 24 may be shielded. Since it is a significantadvantage of the inventive system to provide a very small camera headthat can be easily maneuvered to inspect tight spaces, increasing thedimensions of the camera head by adding shielding should be consideredcarefully.

The camera 10 may be mounted on a robotic delivery system that isremotely controlled through the processing module 30 either through anautomated routine or through an operator control device such as ajoystick, trackball or touchpad. (Note that control signals for therobot may also be carried over the high frequency cable 28.) The roboticsystem may be as simple as multi-axis rail-based system, a multi-axisarticulated arm, or a free-moving robotic system, all remotelycontrollable from a location outside of the hazardous environment. Oneexample of such a robotic system is disclosed in U.S. application Ser.No. 13/453,237, which is incorporated herein by reference.

A watertight connector or penetrator provides connection of the camera10 to the high frequency cable 28. Strain relief should preferably beprovided to avoid damaging or stressing the cable when the robot moves.The cable 28 may be on the order of 50 feet or longer to providesufficient isolation of the processing module 30 from the radiationsource. In some environments, where appropriate, high frequency wirelesscommunication means may be used to facilitate unrestricted movement of afree-moving robot.

The processing module 30 may be housed within a workstation locatedon-site outside of and at a safe distance from the high-radiation orother hazardous environment. The workstation may include or be connectedto a data storage unit for storing the collected video (both raw andprocessed) and a user interface such as a monitor or other graphicdisplay that allows the operator to observe in real time and to controlmovement of the robot to inspect desired area. In the illustratedexample, the processed image may be displayed at a graphical userinterface 40 which may be incorporated into the on-site workstation.Additional monitoring capability may be provided by way of a networkconnection 42, for example, a local area network (LAN), wide areanetwork (WAN), or any other network connection as is known in the art,including the worldwide web (WWW), to a remote monitoring station. Rawand processed images may be saved in one or more data storage devices44, which may be physically located near the inspection station and/orat some remote location.

The use of SERDES encoder/decoders 12 and 32 is a key component of theinvention in allowing high speed communication of the signal generatedby the sensor 20 to the processing module 30. The high speedcommunication provides for very high speed transfer of image data to aremotely-located processor, thus allowing radiation-sensitiveelectronics components to be isolated from the high-radiationenvironment. The inventive system permits real time viewing of the areaunder inspection, taking advantage of the superior resolution of digitalimaging devices and high speed data transfer, to provide a significantimprovement over the existing systems.

The following principles were employed in determining the arrangement ofthe system components:

Electronic assemblies that operate in harsh environments tend beexpensive. The greater the component count, the greater the cost and thegreater the likelihood of failure. Testing IC's which are intended foroperation in harsh environments can be costly and uncertain when thesupport electronics is subject to the same stresses as the unit undertest (UUT). To the extent the IC which must be subjected to stress canbe isolated, system cost can be reduced and reliability improved;assurance in test is also improved.

The conventional method of testing digital integrated circuits (IC's),illustrated in FIG. 3, is by generating test vectors 50 to stimulate thedevices 52 and verifying the resulting outputs 54. This method is firstused in simulation where the device model is commonly referred to as the“unit under test” (“UUT”). Typically the part is modeled—actuallydeveloped—using hardware description language (HDL). The resulting modelis subjected to register level transfer (RTL) verification and itsoperation characterized. Subsequent to RTL level verification, processspecific device models are used to perform timing simulation prior tothe process commonly referred to as “tape out” of the new IC. “Tape out”is the production of the first prototype wafer lots. These wafer lotsare then tested with the same set of test vectors, used in testing ofthe original device models, to characterize the actual components.

One application in which failure of electronic components isparticularly of concern is high radiation environments, such as nuclearreactors. Electronic devices such as sensors, cameras and safetyequipment must be radiation hardened to ensure reliable performance.Schwank, et al. provide an overview of radiation hardness testing ofmicroelectronic devices and ICs in “Radiation hardness Assurance Testingof Microelectronic Devices and Integrated Circuits: RadiationEnvironments, Physical Mechanisms, and Foundations for HardnessAssurance”, Sandia National Laboratories Documents SAND-2008-6851P,which is incorporated herein by reference.

FIG. 4 illustrates a method of operating an IC 72 remotely in a mannerthat allows it to perform most or all of the same functions that itwould perform if it were a part of a single circuit card assembly (CCA)according to standard testing methods. The input signals 60 to be usedfor testing are input into the test waveform generator 62, such as amicro-sequencer or a gate array, which produces the test waveforms 64.The test waveforms are input into SERDES 66 for encoding of thewaveforms into serial bits for high frequency transmission. The encodedsignal is communicated via transmission medium 68, which can be anyconventional communication medium including optical, wired or wireless,to SERDES 70, which decodes the encoded waveforms to provide inputs 74for testing the UUT, i.e., IC 72. The responses 76 produced by IC 72 areconverted by SERDES 70 into a high frequency bit stream for transmissionover medium 68 to SERDES 66. The encoded signal is deserialized bySERDES 66 to produce the received waveforms 78 corresponding to theresponses of the IC 72 to the test waveforms. The received waveforms aredecoded at decoder 80 to generate an output signal 82. As is known inthe art, appropriate clock signals must be provided to each device toenable encoding and decoding.

Features of the described testing scheme include:

-   1. Use of the characterization of the UUT to produce operational    drive waveforms the results of which can be decoded and used by the    receiver in an inherently “error-free” or usable manner as though    the UUT were local to system;-   2. Minimization of part count in the assembly that is exposed to the    harsh environment for improved reliability and reduced cost;-   3. Use of the serialization and transmission for synchronous control    signals and not only payload data as is the practice in conventional    testing methods.

This testing scheme can be expanded so that the source drivingelectronics can be used to drive multiple ICs 90A, 90B, 90C to be tested(UUTs). One possible example is shown in FIG. 5, where the UUTs can senddata to multiple receive waveform decoders (RWDs), e.g., RWD 94 and RWD102, where RWD 102 is remote from the transmit waveform generator (TWG)92 or principal node.

The isolation of sensitive electronic components from hazardousenvironmental conditions is an important aspect of the invention. Whilesignificant advantage is gained through use of the present invention forvisual inspection of nuclear reaction, the invention is not intended tobe limited to such applications. The principles of the invention areapplicable to other sensor types and different environmental situations.Such other uses for the system described herein will become apparent tothose of skill in the art.

1. A camera system for use in a high-radiation environment, comprising:a camera assembly comprising a housing; an image sensor disposed withinthe housing, the image sensor adapted for generating a digital signalcorresponding to a detected image of an object; and a firstserializer/deserializer (SERDES) disposed within the housing forconverting the signal from the image sensor into a serial bit stream; atransmission medium for transmitting the serial bit stream; and an imageprocessing module disposed outside of the high-radiation environment forreceiving the transmitted serial bit stream, the image processing modulecomprising: a second SERDES adapted for deserializing the serial bitstream to generate a decoded image signal; and an image processoradapted to process the decoded image signal to generate an output at adisplay device corresponding to the detected image.
 2. The camera systemof claim 1, wherein the housing comprises a seal for enclosing the imagesensor and the first SERDES in a watertight enclosure.
 3. The camerasystem of claim 1, wherein the housing is formed from stainless steel.4. The camera system of claim 1, wherein the housing comprises radiationshielding enclosing one or more of the image sensor and the firstSERDES.
 5. The camera system of claim 1, wherein the display device isincorporated within an inspection workstation and wherein the inspectionworkstation comprises a controller for controlling operation of thecamera assembly.
 6. The camera system of claim 5, further comprising arobotic delivery system responsive to the controller.
 7. The camerasystem of claim 1, wherein the image sensor comprises a CMOS sensor. 8.The camera system of claim 1, wherein the image sensor isradiation-hardened.
 9. The camera system of claim 1, wherein the imagesensor is a color image sensor.
 10. The camera system of claim 1,wherein the transmission medium is a high-frequency cable.
 11. A camerasystem for use in a hazardous underwater environment, comprising: acamera assembly comprising: a housing having a watertight seal; an imagesensor disposed within the housing, the image sensor adapted forgenerating a digital signal corresponding to an image of an objectlocated within the underwater environment; and a firstserializer/deserializer (SERDES) disposed within the housing forconverting the signal from the image sensor into a serial bit stream; atransmission medium for transmitting the serial bit stream; and an imageprocessing module for receiving the transmitted serial bit stream, theimage processing module comprising: a second SERDES adapted fordeserializing the serial bit stream to generate a decoded image signal;and an image processor adapted to process the decoded image signal togenerate an output at a display device corresponding to the image of theobject.
 12. The camera system of claim 11, wherein the housing is formedfrom stainless steel.
 13. The camera system of claim 11, wherein thehousing comprises radiation shielding enclosing one or more of the imagesensor and the first SERDES.
 14. The camera system of claim 11, whereinthe display device is incorporated within an inspection workstation andwherein the inspection workstation comprises a controller forcontrolling operation of the camera assembly.
 15. The camera system ofclaim 14, further comprising a robotic delivery system responsive to thecontroller.
 16. The camera system of claim 11, wherein the image sensorcomprises a CMOS sensor.
 17. The camera system of claim 11, wherein theimage sensor is radiation-hardened.
 18. The camera system of claim 11,wherein the transmission medium is a high-frequency cable.